We've got a range right off the end of our runway - use it as a visual reference. And every AF base has a shooting range within ~a mile.
I guess it would be a problem if guys were trying 5-mile shots with 45 degree elevation setups... right... In that case, I'd be more worried about living in nearby neighborhoods.
For that matter, we ought to ban all flying over the Southern US during/around May 5, when the flyers go out urging folks not to shoot into the air.
And if some joker's going to try to shoot down a plane with small arms, he's not going to buy a gun range membership. Plenty of other places he could set up somewhat unobserved and try for the golden BB shot.
And let's look at the shot dynamics on that anyhow. I'm an OK shot in large bore. For a long hunting shot at 300 yards, I train to a 4" circle on a stationary target w/a 300WM. Supported with a bench rest I can probably get better, and I'm sure some guy with a nice .50 on a bipod can do even better, but you're planning a shot on a moving target.
So now you're planning to hit an airliner taking off on a ~10 degree climb, airborne 2,000' before the departure end. You manage to get a setup 1/2 mile from the runway, dead-on. You're waiting for him to get to 300 yards for your shot.
That shot happens when the aircraft goes right over your nugget at 200 knots, about 350fps. Go for it, sniper-boy.
So you wait till the next day and turn around to catch the guy on a 3 degree approach. Much easier, right?
At 300 yards, he's approaching now at a leisurely 300fps, but with a pretty impressive angular acceleration as he flies overhead. As a comparison, consider that most of us feel pretty good if we can limit in dove season (15 birds) inside a container of 25 shells. They're moving at ~30 knots and we're shooting at around 20 yards. You're trying to hit a target moving 5 times the speed at 15 times the distance - with a bullet, not a cloud of #8 shot. If you make that shot, and somehow find a vital spot, you've got a good chance to get your own sport shooting show on OLN once your lawyer gets you acquitted.